STU Option

[z3papa]

Not saying I'm moving from FS, but if you prepared a car for STU, what all would you do beyond this:

In my opinion, the biggest downside is the weight. So for diet purposes, I view these as necessary:

Weight/Diet
Lightweight seats/mounts/sliders -- this can easily drop out 100# or 50# per side from the stock power/heated seats if you keep to the 25# min. requirement.

Lightweight battery - this can drop as many as 30-35# depending on how ridiculous you want to go.

Exhaust -- this can bring both hp and weight loss of roughly 45# if done correctly provided you want to be able to drive to an event without headphones on to kill the sound.

Wheels/Tires
Dependent on allowances, I think you can get 18x10.5 or 11's out back and certainly 18x10 out front. What tire allowances are currently still in flux.

Suspension --
Definitely DA coil overs, preferably MCS or AST or 2800 series Koni with Vorshlag camber plates.

Delrin bushings

Engine

CAI -- because we always need a little more sound and breathing

Pulleys -- reduce parasitic loss

Any other ideas or thoughts is this just plain stupid....much like any discussion in the silly season. For anyone interested in the midwest, my local club, Champaign County Sports Car Club, has events into mid November for those with thick skins and no fear of winter flare ups.

[Richbot]

Brakes are worth a chunk of weight. Have to choose carefully given the rules. Maybe just RB and/or pfc rotors. But the stock calipers are also heavy.

Plenty of room for 11's in back and 10.5's in front or 10.5's all around.

Battery would allow for more like 50-60lb with even the largest li-ion, stock is over 70lb.

Pulleys are worth something Would look at an e85 tune if legal can't recall what the ruling was on that. Lots of power to be had if the car consistently hits timing targets instead of pulling timing constantly

Other than that, fun car that will get demolished by a prepped C5. Too tall and too heavy to compete.

[Melchior]

I ran my car at One Lap of America in "STU" trim with aero and without back seats. I was planning to then run the car a local autocrosses and run at nationals in STU. That never happened because I never bought a set of RE71Rs, so I ran my friends E36 in SM at nats instead.

My car weighed 3265 lbs without back seats and with aero (almost no fuel) for OLOA. Adding the weight of the seats back in, and subtracting the aero puts my DCT coupe at ~3315lbs in STU. A manual can get ~44 lbs lighter, and a no option car get even lighter.

2011 E92 M3 DCT
Carbon roof

Engine
-AFE intake
-AA pulley
-Challenge street Xpipe with HFCs
-Titanium Exhaust (18lbs total weight)
-BPM tune

Suspension
-KW Clubsports w/tophats
-custom spring rates
-Eibach front swaybar
-Stoptech front BBK ST40
-OEM rear brakes
-Apex ARC8 18x10.5 +27 on all 4 corners
-285/30r18 Dunlop ZII*

Weight
-Recaro SPGs
-7 lb Deka battery


An Xpipe is worth the whp and weight savings, and should be STU legal (read yourself, it's been a while). A no limits build could saves few more lbs, but not much more power to be had.

My thrust curves show the E92 has the best 2nd gear thrust compared to the 350z and Corvette, so the struggle will be putting the power down to take advantage. The car will weight about 200 lbs more than the winning 350z on equal wheels and tires, and you have McPherson compared to dual aarms. Still, the car is equal in width to the 350z, and narrower than the corvette by 2". I think it's competitive locally, and a top trophy car nationally if someone goes all out.

[Richbot]

I think thrust and tire to weight can be equal or superior and it won't matter if the car is half a foot taller. That's a big dynamic problem that is unsolvable. Still I agree the field is spread enough for just about anything that can get in the ballpark including this car to sneak a trophy with good prep and driving. I'm a big fan of building it and see what happens who cares if it "can't win" see my A-stock thread, heh

Does STU still require the rotors be as big or bigger than stock? If so that rules out the 355mm stop tech kit (stock is 360). I think it would be a weenie protest as the rotors are 7mm thicker than sock but hey it's silly season

[Visceral]

Well, Chris Mayfield won STU at Nats last year in an E92, so it can be done...

[fsmtnbiker]

Originally Posted by Visceral

Well, Chris Mayfield won STU at Nats last year in an E92, so it can be done...

And I did it using Melchior 's car more or less in the spec he posted above (265 yokos instead of 285 re71s/z2*). I've since changed a ton of parts on it because I like to spend lots of money to make the car go no faster.

A local friend here in CA built a no options 6-sp and its <3300lbs.

[Kelse92]

My car is STU setup.
Currently the following:
3450 lbs with low fuel no driver. Full weight DCT/Sunroof fully optioned car
Stoptech ST-60 up front, stock rear
OMP front seats on OEM sliders weigh 32lbs to be STU legal
KW Clubsports with custom spring rates
Hotchkiss front sway bar
Macht-Schnell Intake
Active Autowerke catless X-pipe with 300-cel HFC’s added in an STU legal place
Gintani Muffler
Gintani Tune
Lightweight battery

Current wheel and tire setup on my car is 18x10.5 and 18x11 staggered with Yoko’s. If they change the wheel/tire rules (please write a letter in support!) I will likely do 295’s square or try to figure out setup on 295/315’s.

Some of my coming soon mods are pulley, all power flex bushings, and extra cooling but the cooling is mainly for track use.

If you wanted to get spendy...I think headers could be done legallly, possibly the Karbonius box, upgraded diff of course.

Car is competitive, but depending on how rules shake out I would maybe go for an M2 or Fiata...

[dparm]

Is this STU for NASA?

[fsmtnbiker]

Originally Posted by dparm

Is this STU for NASA?

SCCA Autocross

[ThunderMoose]

Originally Posted by dparm

Is this STU for NASA?

There isn't an STU in NASA. It's just SU to avoid confusion with SCCA STU.

[dparm]

Originally Posted by ThunderMoose

There isn't an STU in NASA. It's just SU to avoid confusion with SCCA STU.

Oh, duh. Thanks.

[Visceral]

I have a similar-ish setup, but I have yet to do the seats and battery.

Which spring rates are you using?

Originally Posted by Kelse92

My car is STU setup.
Currently the following:
3450 lbs with low fuel no driver. Full weight DCT/Sunroof fully optioned car
Stoptech ST-60 up front, stock rear
OMP front seats on OEM sliders weigh 32lbs to be STU legal
KW Clubsports with custom spring rates
Hotchkiss front sway bar
Macht-Schnell Intake
Active Autowerke catless X-pipe with 300-cel HFC’s added in an STU legal place
Gintani Muffler
Gintani Tune
Lightweight battery

Current wheel and tire setup on my car is 18x10.5 and 18x11 staggered with Yoko’s. If they change the wheel/tire rules (please write a letter in support!) I will likely do 295’s square or try to figure out setup on 295/315’s.

Some of my coming soon mods are pulley, all power flex bushings, and extra cooling but the cooling is mainly for track use.

If you wanted to get spendy...I think headers could be done legallly, possibly the Karbonius box, upgraded diff of course.

Car is competitive, but depending on how rules shake out I would maybe go for an M2 or Fiata...

[Kelse92]

Originally Posted by Visceral

I have a similar-ish setup, but I have yet to do the seats and battery.

Which spring rates are you using?

I'm on 515f/800r I did the shorter eibach conversion and that is the rate of those springs up front. It's a bit under-sprung up front so I've been compensating with the Hotchkiss bar set one hole from stiffest but I'm going to look at either finding a different set of coilovers completely soon or rebuilding and making some changes to the KW's including upping the rates all around and I haven't quite decided on what route I'm going to go on that yet.

[Visceral]

Originally Posted by Kelse92

I'm on 515f/800r I did the shorter eibach conversion and that is the rate of those springs up front. It's a bit under-sprung up front so I've been compensating with the Hotchkiss bar set one hole from stiffest but I'm going to look at either finding a different set of coilovers completely soon or rebuilding and making some changes to the KW's including upping the rates all around and I haven't quite decided on what route I'm going to go on that yet.

I can't recommend the MCS (even the 2wNR) enough. Really refined firm ride, like a Porsche RS.

[Visceral]

Originally Posted by fsmtnbiker

And I did it using Melchior 's car more or less in the spec he posted above (265 yokos instead of 285 re71s/z2*). I've since changed a ton of parts on it because I like to spend lots of money to make the car go no faster.

A local friend here in CA built a no options 6-sp and its <3300lbs.

That's significantly lighter than an M2. Were the Yokos square? Why not 275 or 285?

[Kelse92]

Originally Posted by Visceral

That's significantly lighter than an M2. Were the Yokos square? Why not 275 or 285?

I think I lightweight optioned M2 with weight reduction in STU trim could be a pretty serious contender though just in power delivery. The turbo cars are just much more tunable.

And for the A052’s the sizing is tough. 265/35/18 is the best available 18” size they sell in STU rules. They have a 275/40/18 that is reallllyy y’all and difficult to make fit. I test fit one and it will not under any circumstance fit the front unless you cut the body seams etc which is not STU legal.
They make a 285 in a 20” size, but who’s going to run that? Maybe, maybe a Corvette owner.
Next available size is a 295/30/18 which would be ideal but not class legal.
Of the 200tw options for autocross the Yokohama is pretty much the fastest tire available if you can make it work on your car

[Visceral]

Originally Posted by Kelse92

I think I lightweight optioned M2 with weight reduction in STU trim could be a pretty serious contender though just in power delivery. The turbo cars are just much more tunable.

And for the A052’s the sizing is tough. 265/35/18 is the best available 18” size they sell in STU rules. They have a 275/40/18 that is reallllyy y’all and difficult to make fit. I test fit one and it will not under any circumstance fit the front unless you cut the body seams etc which is not STU legal.
They make a 285 in a 20” size, but who’s going to run that? Maybe, maybe a Corvette owner.
Next available size is a 295/30/18 which would be ideal but not class legal.
Of the 200tw options for autocross the Yokohama is pretty much the fastest tire available if you can make it work on your car

Ah, OK. Thanks. I didnt know there wasnt a 275/35-18 option.

I agreee the M2 can scoot, but its tall and heavy... especially for a "2"

[Visceral]

The Yoko 265 has a .1" smaller tread width according to tire rack than the RE71R 275 and a .3" smaller section width, and a .2" smaller diameter. Sounds really close. Also shows an 8/32 tread as opposed to the RE71R 7/32".

[Visceral]

I have a weird feeling that my installed stock bumpstops are messing things up. I had forgotten they're there.

[Richbot]

I used factory bumpstops with my MCS 2-way setup in FS/AS - but that was because the stock springs are basically just there to keep the car from hitting the ground when it was parked

The factory bumpstops are very well-engineered, progressive things, but you're probably using them a lot - are they touching the shock body already when you're on the ground?

[Visceral]

Are solid subframe bushings legal in STU? That strikes me as a suspension part....

nevermind :-/

K. Subframe mount bushings may be replaced, but must attach in the standard location(s) without additional modification or changes. Subframe
position may not be changed. The amount of metal in a replacement
bushing may not be increased relative to the amount of metal found in
a standard bushing for the particular application. Solid metal bushings
are specifically prohibited.

[Richbot]

That specifically allows solid non-metal subframe bushes. You could definitely use the Powerflex subframe bushes. You're probably adding metal with the Turner Delrin bushings as they haver a pretty hefty metal insert. If you are worried about a difficult protest, measure the size of the metal insert that comes with the Powerflex, and measure the OEM (which also has a significant metal insert) and if the powerflex is smaller diameter, you're definitely good to go to the letter and spirit of the rules. The turner one seems to have a pretty substantial increase in metal on one end of the insert which to me is not within the spirit of the rules, but might meet the letter depending on how you measure and define the "amount"

https://www.turnermotorsport.com/p-1...e82-1m-e9x-m3/

https://www.ecstuning.com/b-genuine-...RoCUkEQAvD_BwE

https://www.bimmerworld.com/Suspensi...treet-Kit.html

But honestly it's pretty hard to define that. The stock bshing has a lot of metal in it. There really isnt' that much rubber in it, it's just pretty soft rubber so that the subframe is free to move about the cabin a bit